Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Amortized cost of fixed maturities	$ 7,358.2	$ 6,692.7
Allowance for credit losses	(7.5)	(3.3)	$ 0.0
Cost of equity securities	618.7	684.1
Premium Receivable, Allowance for Credit Loss	13.6	20.9	$ 22.3
Long-term Debt, Current and Non-current	$ 1,152.1	$ 1,247.8
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares outstanding (in shares)	63,684,628	65,436,207